Water scarcity is a major issue in today’s development agenda (Falkenmark, 1997; Savenije, 2000; Rijsberman, 2006; Davies and Simonovic, 2011). For sub-Saharan Africa in particular, several authors predict dramatic water shortages in the coming years (CAWMA, 2007; Davies and Simonovic, 2011) and this is likely to be exacerbated by the complications of managing river basins that cross international borders (Savenije and van der Zaag, 2000). The major issue in sharing an international water resources system is its utter scale and the opaqueness of system interactions over large distances (upstream and downstream). For example, it is difficult to attribute and quantify the consequences of upstream land use changes on downstream flood levels (Carmo Vaz and Lopes Pereira, 2000; Carmo Vaz and Van Der Zaag, 2003; Sengo et al., 2005). This opaqueness may result in unexpected negative consequences of human interventions that are difficult to correct and may augment tensions between riparian countries sharing the basin’s resources.